<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]-->
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="Asciidoctor 1.5.5">
<meta name="author" content="2019-08-08 13:15:33 CEST">
<title>N4JS Language Specification</title>
<link rel="stylesheet" href="styles/spec.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.6.3/css/font-awesome.min.css">
<!-- ************* docinfo ******************************************************************* -->


<!-- ************* Favicon ************-->
<link rel="icon" href="images/favicon.ico" />

<!-- ************* Back-to-top JQuery ************* -->
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<script src="https://code.jquery.com/ui/1.12.0/jquery-ui.js"></script>


<link href="styles/prism.min.css" rel="stylesheet" />
<script type="text/javascript" async
  src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/MathJax.js?config=TeX-MML-AM_CHTML">
</script>

<!-- ************* Styles ************* -->
<link rel="stylesheet" type="text/css" href="styles/n4jsspec-adoc.css">


<!-- ****************** NavBar ****************** -->
<div id="menubar">
	<div class="banner">
        <a href="https://www.eclipse.org/n4js/#"><img id="logo" src="images/n4js-logo.png" alt="Eclipse N4JS"></a>
    </div>
<ul>
  <li><a href="index.html">Index</a></li>
</ul>
</div>
<!-- ************* docinfo ******************************************************************* -->
<style>
      .admonitionblock td.icon .icon-todo:before{content:"\f249";color:#f4ee42}
    </style>
</head>
<body class="book toc2 toc-left">
<div id="header">
<h1>N4JS Language Specification</h1>
<div class="details">
<span id="author" class="author">2019-08-08 13:15:33 CEST</span><br>
<span id="revnumber">version 0.9</span>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="introduction.html#_introduction">1. Introduction</a>
<ul class="sectlevel2">
<li><a href="introduction.html#_notation">1.1. Notation</a>
<ul class="sectlevel3">
<li><a href="introduction.html#_grammar-notation">1.1.1. Grammar Notation</a></li>
<li><a href="introduction.html#_type-judgments-and-rules-and-constraints-notation">1.1.2. Type Judgments and Rules and Constraints Notation</a>
<ul class="sectlevel4">
<li><a href="introduction.html#_typing-rules-and-judgments">1.1.2.1. Typing Rules and Judgments</a></li>
<li><a href="introduction.html#_types-of-an-element">1.1.2.2. Types of an Element</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="introduction.html#_auxiliary-functions">1.2. Auxiliary Functions</a>
<ul class="sectlevel3">
<li><a href="introduction.html#_binding">1.2.1. Binding</a></li>
<li><a href="introduction.html#_merging-types">1.2.2. Merging Types</a>
<ul class="sectlevel4">
<li><a href="introduction.html#_logic-formulas">1.2.2.1. Logic Formulas</a></li>
</ul>
</li>
<li><a href="introduction.html#_symbols-and-font-convention">1.2.3. Symbols and Font Convention</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="grammar.html#_grammar">2. Grammar</a>
<ul class="sectlevel2">
<li><a href="grammar.html#_lexical-conventions">2.1. Lexical Conventions</a>
<ul class="sectlevel3">
<li><a href="grammar.html#_identifier-names-and-identifiers">2.1.1. Identifier Names and Identifiers</a></li>
<li><a href="grammar.html#_this-keyword">2.1.2. This Keyword</a></li>
<li><a href="grammar.html#_regular-expression-literals">2.1.3. Regular Expression Literals</a></li>
<li><a href="grammar.html#_automatic-semicolon-insertion">2.1.4. Automatic Semicolon Insertion</a></li>
<li><a href="grammar.html#_jsdoc">2.1.5. JSDoc</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="names.html#_names">3. Names</a>
<ul class="sectlevel2">
<li><a href="names.html#_access-control">3.1. Access Control</a></li>
<li><a href="names.html#_accessibility-of-types-top-level-variables-and-function-declarations">3.2. Accessibility of Types, Top-Level Variables and Function Declarations</a>
<ul class="sectlevel3">
<li><a href="names.html#_accessibility-of-members">3.2.1. Accessibility of Members</a></li>
<li><a href="names.html#_valid-names">3.2.2. Valid Names</a></li>
<li><a href="names.html#_qualified-names">3.2.3. Qualified Names</a></li>
<li><a href="names.html#_name-duplicates">3.2.4. Name Duplicates</a>
<ul class="sectlevel4">
<li><a href="names.html#_lexical-environment">3.2.4.1. Lexical Environment</a></li>
<li><a href="names.html#_duplicates-and-shadowing">3.2.4.2. Duplicates and Shadowing</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="types.html#_types">4. Types</a>
<ul class="sectlevel2">
<li><a href="types.html#_overview">4.1. Overview</a></li>
<li><a href="types.html#_type-expressions">4.2. Type Expressions</a>
<ul class="sectlevel3">
<li><a href="types.html#_syntax">4.2.1. Syntax</a></li>
<li><a href="types.html#_properties">4.2.2. Properties</a></li>
<li><a href="types.html#_semantics">4.2.3. Semantics</a></li>
</ul>
</li>
<li><a href="types.html#_type-inference">4.3. Type Inference</a></li>
<li><a href="types.html#_generic-and-parameterized-types">4.4. Generic and Parameterized Types</a>
<ul class="sectlevel3">
<li><a href="types.html#_generic-types">4.4.1. Generic Types</a></li>
<li><a href="types.html#_type-variables">4.4.2. Type Variables</a></li>
<li><a href="types.html#_parameterized-types">4.4.3. Parameterized Types</a></li>
</ul>
</li>
<li><a href="types.html#_primitive-ecmascript-types">4.5. Primitive ECMAScript Types</a>
<ul class="sectlevel3">
<li><a href="types.html#_undefined-type">4.5.1. Undefined Type</a></li>
<li><a href="types.html#_null-type">4.5.2. Null Type</a></li>
<li><a href="types.html#_primitive-boolean-type">4.5.3. Primitive Boolean Type</a></li>
<li><a href="types.html#_primitive-string-type">4.5.4. Primitive String Type</a></li>
<li><a href="types.html#_primitive-number-type">4.5.5. Primitive Number Type</a></li>
<li><a href="types.html#_primitive-type-int">4.5.6. Primitive Type int</a></li>
<li><a href="types.html#_primitive-symbol-type">4.5.7. Primitive Symbol Type</a></li>
</ul>
</li>
<li><a href="types.html#_primitive-n4js-types">4.6. Primitive N4JS Types</a>
<ul class="sectlevel3">
<li><a href="types.html#_any-type">4.6.1. Any Type</a>
<ul class="sectlevel4">
<li><a href="types.html#any-type-semantics">4.6.1.1. Semantics</a></li>
<li><a href="types.html#any-type-type-inference">4.6.1.2. Type Inference</a>
<ul class="sectlevel5">
<li><a href="types.html#_default-type-of-variables">4.6.1.2.1. Default Type of Variables</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="types.html#_void-type">4.6.2. Void Type</a>
<ul class="sectlevel4">
<li><a href="types.html#void-type-semantics">4.6.2.1. Semantics</a></li>
</ul>
</li>
<li><a href="types.html#_unknown-type">4.6.3. Unknown Type</a></li>
<li><a href="types.html#_primitive-pathselector-and-i18nkey">4.6.4. Primitive Pathselector and I18nKey</a>
<ul class="sectlevel4">
<li><a href="types.html#pathselector-semantics">4.6.4.1. Semantics</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="types.html#_built-in-ecmascript-object-types">4.7. Built-in ECMAScript Object Types</a>
<ul class="sectlevel3">
<li><a href="types.html#ECMAScript-objects-semantics">4.7.1. Semantics</a></li>
<li><a href="types.html#_object-type">4.7.2. Object Type</a></li>
<li><a href="types.html#_function-object-type">4.7.3. Function-Object-Type</a></li>
<li><a href="types.html#_array-object-type">4.7.4. Array Object Type</a></li>
<li><a href="types.html#_string-object-type">4.7.5. String Object Type</a></li>
<li><a href="types.html#_boolean-object-type">4.7.6. Boolean Object Type</a></li>
<li><a href="types.html#_number-object-type">4.7.7. Number Object Type</a></li>
<li><a href="types.html#_global-object-type">4.7.8. Global Object Type</a></li>
<li><a href="types.html#_symbol">4.7.9. Symbol</a></li>
<li><a href="types.html#_promise">4.7.10. Promise</a></li>
<li><a href="types.html#_iterator-interface">4.7.11. Iterator Interface</a></li>
<li><a href="types.html#_iterable-interface">4.7.12. Iterable Interface</a></li>
</ul>
</li>
<li><a href="types.html#_built-in-n4js-types">4.8. Built-In N4JS Types</a>
<ul class="sectlevel3">
<li><a href="types.html#_n4object">4.8.1. N4Object</a>
<ul class="sectlevel4">
<li><a href="types.html#N4Object-semantics">4.8.1.1. Semantics</a></li>
</ul>
</li>
<li><a href="types.html#_n4class">4.8.2. N4Class</a></li>
<li><a href="types.html#IterableN">4.8.3. IterableN</a></li>
</ul>
</li>
<li><a href="types.html#_type-modifiers">4.9. Type Modifiers</a>
<ul class="sectlevel3">
<li><a href="types.html#Type_Modifiers_Dynamic">4.9.1. Dynamic</a></li>
<li><a href="types.html#_optional-return-types">4.9.2. Optional Return Types</a></li>
</ul>
</li>
<li><a href="types.html#_union-and-intersection-type-composed-types">4.10. Union and Intersection Type (Composed Types)</a>
<ul class="sectlevel3">
<li><a href="types.html#_union-type">4.10.1. Union Type</a>
<ul class="sectlevel4">
<li><a href="types.html#union-type-syntax">4.10.1.1. Syntax</a></li>
<li><a href="types.html#union-type-semantics">4.10.1.2. Semantics</a></li>
<li><a href="types.html#_warnings">4.10.1.3. Warnings</a></li>
</ul>
</li>
<li><a href="types.html#_intersection-type">4.10.2. Intersection Type</a>
<ul class="sectlevel4">
<li><a href="types.html#intersection-type-syntax">4.10.2.1. Syntax</a></li>
<li><a href="types.html#intersection-type-semantics">4.10.2.2. Semantics</a></li>
<li><a href="types.html#_warnings-2">4.10.2.3. Warnings</a></li>
</ul>
</li>
<li><a href="types.html#_composed-types-in-wildcards">4.10.3. Composed Types in Wildcards</a></li>
<li><a href="types.html#_property-access-for-composed-types">4.10.4. Property Access for Composed Types</a>
<ul class="sectlevel4">
<li><a href="types.html#_properties-of-union-type">4.10.4.1. Properties of Union Type</a>
<ul class="sectlevel5">
<li><a href="types.html#_remarks-on-union-type-s-members">4.10.4.1.1. Remarks on union type’s members:</a></li>
</ul>
</li>
<li><a href="types.html#_properties-of-intersection-type">4.10.4.2. Properties of Intersection Type</a>
<ul class="sectlevel5">
<li><a href="types.html#_remarks-on-intersection-type-s-methods">4.10.4.2.1. Remarks on intersection type’s methods:</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="types.html#_constructor-and-classifier-type">4.11. Constructor and Classifier Type</a>
<ul class="sectlevel3">
<li><a href="types.html#_syntax-3">4.11.1. Syntax</a></li>
<li><a href="types.html#_semantics-2">4.11.2. Semantics</a></li>
<li><a href="types.html#_constructors-and-prototypes-in-ecmascript-2015">4.11.3. Constructors and Prototypes in ECMAScript 2015</a></li>
</ul>
</li>
<li><a href="types.html#_this-type">4.12. This Type</a>
<ul class="sectlevel3">
<li><a href="types.html#this-type-syntax">4.12.1. Syntax</a></li>
<li><a href="types.html#this-keyword-semantics">4.12.2. Semantics</a></li>
</ul>
</li>
<li><a href="types.html#_enums">4.13. Enums</a>
<ul class="sectlevel3">
<li><a href="types.html#_enums-n4js">4.13.1. Enums (N4JS)</a>
<ul class="sectlevel4">
<li><a href="types.html#enums-syntax">4.13.1.1. Syntax</a></li>
<li><a href="types.html#enums-semantics">4.13.1.2. Semantics</a></li>
</ul>
</li>
<li><a href="types.html#_string-based-enums">4.13.2. String-Based Enums</a></li>
</ul>
</li>
<li><a href="types.html#_short-hand-syntax">4.14. Short-Hand Syntax</a>
<ul class="sectlevel3">
<li><a href="types.html#_array-short-hand-syntax">4.14.1. Array Short-Hand Syntax</a></li>
<li><a href="types.html#_iterablen-short-hand-syntax">4.14.2. IterableN Short-Hand Syntax</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="classifiers.html#_classifiers">5. Classifiers</a>
<ul class="sectlevel2">
<li><a href="classifiers.html#_n4js-specific-classifiers">5.1. N4JS Specific Classifiers</a>
<ul class="sectlevel3">
<li><a href="classifiers.html#_properties-2">5.1.1. Properties</a></li>
<li><a href="classifiers.html#_common-semantics-of-classifiers">5.1.2. Common Semantics of Classifiers</a></li>
<li><a href="classifiers.html#_classes">5.1.3. Classes</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_definition-of-classes">5.1.3.1. Definition of Classes</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#class-syntax">5.1.3.1.1. Syntax</a></li>
<li><a href="classifiers.html#class-properties">5.1.3.1.2. Properties</a></li>
<li><a href="classifiers.html#class-type-inference">5.1.3.1.3. Type Inference</a></li>
</ul>
</li>
<li><a href="classifiers.html#class-semantics">5.1.3.2. Semantics</a></li>
<li><a href="classifiers.html#_final-modifier">5.1.3.3. Final Modifier</a></li>
<li><a href="classifiers.html#_abstract-classes">5.1.3.4. Abstract Classes</a></li>
<li><a href="classifiers.html#_non-instantiable-classes">5.1.3.5. Non-Instantiable Classes</a></li>
<li><a href="classifiers.html#_superclass">5.1.3.6. Superclass</a></li>
</ul>
</li>
<li><a href="classifiers.html#_interfaces">5.1.4. Interfaces</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_definition-of-interfaces">5.1.4.1. Definition of Interfaces</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#interfaces-syntax">5.1.4.1.1. Syntax</a></li>
<li><a href="classifiers.html#interfaces-properties">5.1.4.1.2. Properties</a></li>
<li><a href="classifiers.html#interfaces-type-inference">5.1.4.1.3. Type Inference</a></li>
<li><a href="classifiers.html#interfaces-semantics">5.1.4.1.4. Semantics</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="classifiers.html#_generic-classifiers">5.1.5. Generic Classifiers</a></li>
<li><a href="classifiers.html#sec:definition-site-variance">5.1.6. Definition-Site Variance</a></li>
</ul>
</li>
<li><a href="classifiers.html#_members">5.2. Members</a>
<ul class="sectlevel3">
<li><a href="classifiers.html#_syntax-4">5.2.1. Syntax</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_properties-3">5.2.1.1. Properties</a></li>
</ul>
</li>
<li><a href="classifiers.html#_semantics-3">5.2.2. Semantics</a></li>
<li><a href="classifiers.html#_methods">5.2.3. Methods</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_syntax-5">5.2.3.1. Syntax</a></li>
<li><a href="classifiers.html#_properties-4">5.2.3.2. Properties</a></li>
<li><a href="classifiers.html#_semantics-4">5.2.3.3. Semantics</a></li>
<li><a href="classifiers.html#_final-methods">5.2.3.4. Final Methods</a></li>
<li><a href="classifiers.html#_abstract-methods">5.2.3.5. Abstract Methods</a></li>
<li><a href="classifiers.html#_generic-methods">5.2.3.6. Generic Methods</a></li>
</ul>
</li>
<li><a href="classifiers.html#_default-methods-in-interfaces">5.2.4. Default Methods in Interfaces</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_asynchronous-methods">5.2.4.1. Asynchronous Methods</a></li>
</ul>
</li>
<li><a href="classifiers.html#_constructors">5.2.5. Constructors</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_structural-this-type-in-constructor">5.2.5.1. Structural This Type in Constructor</a></li>
<li><a href="classifiers.html#spec-constructor">5.2.5.2. @Spec Constructor</a></li>
<li><a href="classifiers.html#_callable-constructors">5.2.5.3. Callable Constructors</a></li>
<li><a href="classifiers.html#_covariant-constructors">5.2.5.4. Covariant Constructors</a></li>
</ul>
</li>
<li><a href="classifiers.html#_data-fields">5.2.6. Data Fields</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#data-fields-syntax">5.2.6.1. Syntax</a></li>
<li><a href="classifiers.html#data-fields-properties">5.2.6.2. Properties</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#data-fields-semantics">5.2.6.2.1. Semantics</a></li>
<li><a href="classifiers.html#data-fields-type-inference">5.2.6.2.2. Type Inference</a></li>
</ul>
</li>
<li><a href="classifiers.html#_assignment-modifiers">5.2.6.3. Assignment Modifiers</a></li>
<li><a href="classifiers.html#_field-accessors-getter-setter">5.2.6.4. Field Accessors (Getter/Setter)</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#field-acessors-syntax">5.2.6.4.1. Syntax</a></li>
<li><a href="classifiers.html#field-acessors-properties">5.2.6.4.2. Properties</a></li>
<li><a href="classifiers.html#field-accessors-semantics">5.2.6.4.3. Semantics</a></li>
</ul>
</li>
<li><a href="classifiers.html#optional-fields">5.2.6.5. Optional Fields</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#_syntax-6">5.2.6.5.1. Syntax</a></li>
<li><a href="classifiers.html#_semantics-5">5.2.6.5.2. Semantics</a></li>
<li><a href="classifiers.html#_background">5.2.6.5.3. Background</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="classifiers.html#_static-members">5.2.7. Static Members</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_access-from-and-to-static-members">5.2.7.1. Access From and To Static Members</a></li>
<li><a href="classifiers.html#_generic-static-methods">5.2.7.2. Generic static methods</a></li>
<li><a href="classifiers.html#_static-members-of-interfaces">5.2.7.3. Static Members of Interfaces</a></li>
</ul>
</li>
<li><a href="classifiers.html#_redefinition-of-members">5.2.8. Redefinition of Members</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_overriding-of-members">5.2.8.1. Overriding of Members</a></li>
<li><a href="classifiers.html#_implementation-of-members">5.2.8.2. Implementation of Members</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#_member-consumption">5.2.8.2.1. Member Consumption</a></li>
<li><a href="classifiers.html#_member-implementation">5.2.8.2.2. Member Implementation</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="classifiers.html#_structural-typing">5.3. Structural Typing</a>
<ul class="sectlevel3">
<li><a href="classifiers.html#_syntax-7">5.3.1. Syntax</a></li>
<li><a href="classifiers.html#_definition-site-structural-typing">5.3.2. Definition Site Structural Typing</a></li>
<li><a href="classifiers.html#_use-site-structural-typing">5.3.3. Use-Site Structural Typing</a></li>
<li><a href="classifiers.html#structural-readWriteInit-field-typing">5.3.4. Structural Read-only, Write-only and Initializer Field Typing</a></li>
<li><a href="classifiers.html#_public-setter-annotated-with-code-providesinitializer-code">5.3.5. Public Setter Annotated With <code>ProvidesInitializer</code></a></li>
<li><a href="classifiers.html#_structural-types-with-optional-fields">5.3.6. Structural Types With Optional Fields</a></li>
<li><a href="classifiers.html#_structural-types-with-access-modifier">5.3.7. Structural Types With Access Modifier</a></li>
<li><a href="classifiers.html#_structural-types-with-additional-members">5.3.8. Structural Types With Additional Members</a>
<ul class="sectlevel4">
<li><a href="classifiers.html#_syntax-8">5.3.8.1. Syntax</a>
<ul class="sectlevel5">
<li><a href="classifiers.html#_semantics-6">5.3.8.1.1. Semantics</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="functions.html#_functions">6. Functions</a>
<ul class="sectlevel2">
<li><a href="functions.html#_function-type">6.1. Function Type</a>
<ul class="sectlevel3">
<li><a href="functions.html#_properties-5">6.1.1. Properties</a></li>
<li><a href="functions.html#function-type-inference">6.1.2. Type Inference</a></li>
<li><a href="functions.html#_autoboxing-of-function-type">6.1.3. Autoboxing of Function Type</a></li>
<li><a href="functions.html#_arguments-object">6.1.4. Arguments Object</a></li>
</ul>
</li>
<li><a href="functions.html#_ecmascript-5-function-definition">6.2. ECMAScript 5 Function Definition</a>
<ul class="sectlevel3">
<li><a href="functions.html#_function-declaration">6.2.1. Function Declaration</a>
<ul class="sectlevel4">
<li><a href="functions.html#_syntax-9">6.2.1.1. Syntax</a></li>
<li><a href="functions.html#_semantics-8">6.2.1.2. Semantics</a></li>
</ul>
</li>
<li><a href="functions.html#_function-expression">6.2.2. Function Expression</a>
<ul class="sectlevel4">
<li><a href="functions.html#function-expression-syntax">6.2.2.1. Syntax</a></li>
<li><a href="functions.html#_semantics-and-type-inference">6.2.2.2. Semantics and Type Inference</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="functions.html#_ecmascript-2015-function-definition">6.3. ECMAScript 2015 Function Definition</a>
<ul class="sectlevel3">
<li><a href="functions.html#_formal-parameters">6.3.1. Formal Parameters</a>
<ul class="sectlevel4">
<li><a href="functions.html#Type_Modifiers_Optional">6.3.1.1. Optional Parameters</a></li>
<li><a href="functions.html#Type_Modifiers_Default">6.3.1.2. Default Parameters</a></li>
<li><a href="functions.html#Type_Modifiers_Variadic">6.3.1.3. Variadic</a></li>
</ul>
</li>
<li><a href="functions.html#_generator-functions">6.3.2. Generator Functions</a>
<ul class="sectlevel4">
<li><a href="functions.html#generator-functions-syntax">6.3.2.1. Syntax</a></li>
<li><a href="functions.html#generator-functions-semantics">6.3.2.2. Semantics</a></li>
<li><a href="functions.html#_generator-arrow-functions">6.3.2.3. Generator Arrow Functions</a></li>
</ul>
</li>
<li><a href="functions.html#_arrow-function-expression">6.3.3. Arrow Function Expression</a>
<ul class="sectlevel4">
<li><a href="functions.html#arrow-function-expression-syntax">6.3.3.1. Syntax</a></li>
<li><a href="functions.html#arrow-function-expression-semantics-and-type-inference">6.3.3.2. Semantics and Type Inference</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="functions.html#_ecmascript-proposals-function-definition">6.4. ECMAScript Proposals Function Definition</a>
<ul class="sectlevel3">
<li><a href="functions.html#_asynchronous-functions">6.4.1. Asynchronous Functions</a>
<ul class="sectlevel4">
<li><a href="functions.html#asynchronous-functions-syntax">6.4.1.1. Syntax</a></li>
<li><a href="functions.html#asynchronous-functions-semantics">6.4.1.2. Semantics</a></li>
<li><a href="functions.html#_asynchronous-arrow-functions">6.4.1.3. Asynchronous Arrow Functions</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="functions.html#_n4js-extended-function-definition">6.5. N4JS Extended Function Definition</a>
<ul class="sectlevel3">
<li><a href="functions.html#_generic-functions">6.5.1. Generic Functions</a></li>
<li><a href="functions.html#_promisifiable-functions">6.5.2. Promisifiable Functions</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="conversions_and_reflection.html#_conversions-and-reflection">7. Conversions and Reflection</a>
<ul class="sectlevel2">
<li><a href="conversions_and_reflection.html#_autoboxing-and-coercing">7.1. Autoboxing and Coercing</a>
<ul class="sectlevel3">
<li><a href="conversions_and_reflection.html#_coercing">7.1.1. Coercing</a></li>
<li><a href="conversions_and_reflection.html#_autoboxing-of-primitives">7.1.2. Autoboxing of Primitives</a></li>
<li><a href="conversions_and_reflection.html#_autoboxing-of-function-expressions-and-declarations">7.1.3. Autoboxing of Function Expressions and Declarations</a></li>
</ul>
</li>
<li><a href="conversions_and_reflection.html#_auto-conversion-of-objects">7.2. Auto-Conversion of Objects</a>
<ul class="sectlevel3">
<li><a href="conversions_and_reflection.html#_auto-conversion-of-class-instances">7.2.1. Auto-Conversion of Class Instances</a>
<ul class="sectlevel4">
<li><a href="conversions_and_reflection.html#_auto-conversion-of-interface-instances">7.2.1.1. Auto-Conversion of Interface Instances</a></li>
</ul>
</li>
<li><a href="conversions_and_reflection.html#_auto-conversion-of-enum-literals">7.2.2. Auto-Conversion of Enum Literals</a></li>
</ul>
</li>
<li><a href="conversions_and_reflection.html#_type-cast-and-type-check">7.3. Type Cast and Type Check</a>
<ul class="sectlevel3">
<li><a href="conversions_and_reflection.html#_type-cast">7.3.1. Type Cast</a></li>
<li><a href="conversions_and_reflection.html#_type-check">7.3.2. Type Check</a></li>
</ul>
</li>
<li><a href="conversions_and_reflection.html#_reflection-meta-information">7.4. Reflection meta-information</a>
<ul class="sectlevel3">
<li><a href="conversions_and_reflection.html#_reflection-for-classes">7.4.1. Reflection for Classes</a></li>
<li><a href="conversions_and_reflection.html#_reflection-for-interfaces">7.4.2. Reflection for Interfaces</a></li>
<li><a href="conversions_and_reflection.html#_reflection-for-enumerations">7.4.3. Reflection for Enumerations</a></li>
</ul>
</li>
<li><a href="conversions_and_reflection.html#_conversion-of-primitive-types">7.5. Conversion of primitive types</a></li>
</ul>
</li>
<li><a href="expressions.html#_expressions">8. Expressions</a>
<ul class="sectlevel2">
<li><a href="expressions.html#_ecmascript-5-expressions">8.1. ECMAScript 5 Expressions</a>
<ul class="sectlevel3">
<li><a href="expressions.html#_the-this-literal">8.1.1. The this Literal</a></li>
<li><a href="expressions.html#_identifier">8.1.2. Identifier</a></li>
<li><a href="expressions.html#_literals">8.1.3. Literals</a>
<ul class="sectlevel4">
<li><a href="expressions.html#_integer-literals">8.1.3.1. Integer Literals</a></li>
</ul>
</li>
<li><a href="expressions.html#_array-literal">8.1.4. Array Literal</a></li>
<li><a href="expressions.html#_object-literal">8.1.5. Object Literal</a>
<ul class="sectlevel4">
<li><a href="expressions.html#_properties-6">8.1.5.1. Properties</a></li>
<li><a href="expressions.html#_scoping-and-linking">8.1.5.2. Scoping and linking</a></li>
</ul>
</li>
<li><a href="expressions.html#_parenthesized-expression-and-grouping-operator">8.1.6. Parenthesized Expression and Grouping Operator</a></li>
<li><a href="expressions.html#_property-accessors">8.1.7. Property Accessors</a>
<ul class="sectlevel4">
<li><a href="expressions.html#properties-1">8.1.7.1. Properties</a></li>
</ul>
</li>
<li><a href="expressions.html#_new-expression">8.1.8. New Expression</a></li>
<li><a href="expressions.html#_function-expression-2">8.1.9. Function Expression</a></li>
<li><a href="expressions.html#_function-calls">8.1.10. Function Calls</a></li>
<li><a href="expressions.html#_postfix-expression">8.1.11. Postfix Expression</a></li>
<li><a href="expressions.html#_unary-expression">8.1.12. Unary Expression</a></li>
<li><a href="expressions.html#_multiplicative-expression">8.1.13. Multiplicative Expression</a></li>
<li><a href="expressions.html#_additive-expression">8.1.14. Additive Expression</a>
<ul class="sectlevel4">
<li><a href="expressions.html#type-inference-10">8.1.14.1. Type Inference</a></li>
</ul>
</li>
<li><a href="expressions.html#_bitwise-shift-expression">8.1.15. Bitwise Shift Expression</a></li>
<li><a href="expressions.html#_relational-expression">8.1.16. Relational Expression</a></li>
<li><a href="expressions.html#_equality-expression">8.1.17. Equality Expression</a></li>
<li><a href="expressions.html#_binary-bitwise-expression">8.1.18. Binary Bitwise Expression</a></li>
<li><a href="expressions.html#_binary-logical-expression">8.1.19. Binary Logical Expression</a></li>
<li><a href="expressions.html#_conditional-expression">8.1.20. Conditional Expression</a></li>
<li><a href="expressions.html#_assignment-expression">8.1.21. Assignment Expression</a></li>
<li><a href="expressions.html#_comma-expression">8.1.22. Comma Expression</a></li>
</ul>
</li>
<li><a href="expressions.html#_ecmascript-6-expressions">8.2. ECMAScript 6 Expressions</a>
<ul class="sectlevel3">
<li><a href="expressions.html#_the-super-keyword">8.2.1. The super Keyword</a></li>
</ul>
</li>
<li><a href="expressions.html#_ecmascript-7-expressions">8.3. ECMAScript 7 Expressions</a>
<ul class="sectlevel3">
<li><a href="expressions.html#_await-expression">8.3.1. Await Expression</a></li>
</ul>
</li>
<li><a href="expressions.html#_n4js-specific-expressions">8.4. N4JS Specific Expressions</a>
<ul class="sectlevel3">
<li><a href="expressions.html#_class-expression">8.4.1. Class Expression</a></li>
<li><a href="expressions.html#_cast-as-expression">8.4.2. Cast (As) Expression</a>
<ul class="sectlevel4">
<li><a href="expressions.html#cast-as-expression-semantics-type-inference">8.4.2.1. Semantics and Type Inference</a></li>
</ul>
</li>
<li><a href="expressions.html#Import_Calls">8.4.3. Import Calls</a></li>
</ul>
</li>
<li><a href="expressions.html#compile-time-expressions">8.5. Compile-Time Expressions</a></li>
</ul>
</li>
<li><a href="statements.html#_statements">9. Statements</a>
<ul class="sectlevel2">
<li><a href="statements.html#_ecmascript-5-statements">9.1. ECMAScript 5 Statements</a>
<ul class="sectlevel3">
<li><a href="statements.html#_function-or-field-accessor-bodies">9.1.1. Function or Field Accessor Bodies</a></li>
<li><a href="statements.html#_variable-statement">9.1.2. Variable Statement</a></li>
<li><a href="statements.html#_if-statement">9.1.3. If Statement</a></li>
<li><a href="statements.html#_iteration-statements">9.1.4. Iteration Statements</a></li>
<li><a href="statements.html#_return-statement">9.1.5. Return Statement</a></li>
<li><a href="statements.html#_with-statement">9.1.6. With Statement</a></li>
<li><a href="statements.html#_switch-statement">9.1.7. Switch Statement</a></li>
<li><a href="statements.html#_throw-try-and-catch-statements">9.1.8. Throw, Try, and Catch Statements</a></li>
<li><a href="statements.html#_debugger-statement">9.1.9. Debugger Statement</a></li>
</ul>
</li>
<li><a href="statements.html#_ecmascript-6-statements">9.2. ECMAScript 6 Statements</a>
<ul class="sectlevel3">
<li><a href="statements.html#_let">9.2.1. Let</a></li>
<li><a href="statements.html#_const">9.2.2. Const</a></li>
<li><a href="statements.html#_for-of-statement">9.2.3. <code>for &#8230;&#8203; of</code> statement</a></li>
<li><a href="statements.html#_import-statement">9.2.4. Import Statement</a>
<ul class="sectlevel4">
<li><a href="statements.html#Dynamic_Imports">9.2.4.1. Dynamic Imports</a></li>
<li><a href="statements.html#_immutabilaty-of-imports">9.2.4.2. Immutabilaty of Imports</a></li>
</ul>
</li>
<li><a href="statements.html#_export-statement">9.2.5. Export Statement</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#_annotations">10. Annotations</a>
<ul class="sectlevel2">
<li><a href="#_introduction-2">10.1. Introduction</a>
<ul class="sectlevel3">
<li><a href="#_syntax-13">10.1.1. Syntax</a></li>
<li><a href="#_properties-7">10.1.2. Properties</a></li>
<li><a href="#_element-specific-annotations">10.1.3. Element-Specific Annotations</a></li>
<li><a href="#_general-annotations">10.1.4. General Annotations</a>
<ul class="sectlevel4">
<li><a href="#_idebug">10.1.4.1. IDEBUG</a></li>
</ul>
</li>
<li><a href="#idebug-syntax">10.1.5. Syntax</a>
<ul class="sectlevel4">
<li><a href="#_semantics-11">10.1.5.1. Semantics</a></li>
<li><a href="#_suppress-warnings">10.1.5.2. Suppress Warnings</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#_declaration-of-annotations">10.2. Declaration of Annotations</a></li>
</ul>
</li>
<li><a href="extended_fetaures.html#_extended-fetaures">11. Extended Fetaures</a>
<ul class="sectlevel2">
<li><a href="extended_fetaures.html#_array-and-object-destructuring">11.1. Array and Object Destructuring</a>
<ul class="sectlevel3">
<li><a href="extended_fetaures.html#_syntax-14">11.1.1. Syntax</a></li>
<li><a href="extended_fetaures.html#_semantics-12">11.1.2. Semantics</a></li>
</ul>
</li>
<li><a href="extended_fetaures.html#_dependency-injection">11.2. Dependency Injection</a>
<ul class="sectlevel3">
<li><a href="extended_fetaures.html#_di-components-and-injectors">11.2.1. DI Components and Injectors</a>
<ul class="sectlevel4">
<li><a href="extended_fetaures.html#_dicomponent-relations">11.2.1.1. DIComponent Relations</a></li>
</ul>
</li>
<li><a href="extended_fetaures.html#_binders-and-bindings">11.2.2. Binders and Bindings</a></li>
<li><a href="extended_fetaures.html#_injection-points">11.2.3. Injection Points</a>
<ul class="sectlevel4">
<li><a href="extended_fetaures.html#_field-injection">11.2.3.1. Field Injection</a></li>
<li><a href="extended_fetaures.html#_constructor-injection">11.2.3.2. Constructor Injection</a></li>
<li><a href="extended_fetaures.html#_method-injection">11.2.3.3. Method Injection</a>
<ul class="sectlevel5">
<li><a href="extended_fetaures.html#_provider">11.2.3.3.1. Provider</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="extended_fetaures.html#_n4js-di-life-cycle-and-scopes">11.2.4. N4JS DI Life Cycle and Scopes</a>
<ul class="sectlevel4">
<li><a href="extended_fetaures.html#_injection-cylces">11.2.4.1. Injection Cylces</a></li>
<li><a href="extended_fetaures.html#_default-scope">11.2.4.2. Default Scope</a></li>
<li><a href="extended_fetaures.html#_singleton-scope">11.2.4.3. Singleton Scope</a></li>
<li><a href="extended_fetaures.html#_per-injection-chain-singleton">11.2.4.4. Per Injection Chain Singleton</a></li>
</ul>
</li>
<li><a href="extended_fetaures.html#_validation-of-callsites-targeting-n4injector-methods">11.2.5. Validation of callsites targeting N4Injector methods</a></li>
<li><a href="extended_fetaures.html#_n4js-di-annotations">11.2.6. N4JS DI Annotations</a>
<ul class="sectlevel4">
<li><a href="extended_fetaures.html#_n4js-di-generateinjector">11.2.6.1. N4JS DI @GenerateInjector</a></li>
<li><a href="extended_fetaures.html#_n4js-di-withparentinjector">11.2.6.2. N4JS DI @WithParentInjector</a></li>
<li><a href="extended_fetaures.html#_n4js-di-usebinder">11.2.6.3. N4JS DI @UseBinder</a></li>
<li><a href="extended_fetaures.html#_n4js-di-binder">11.2.6.4. N4JS DI @Binder</a></li>
<li><a href="extended_fetaures.html#_n4js-di-bind">11.2.6.5. N4JS DI @Bind</a></li>
<li><a href="extended_fetaures.html#_n4js-di-provides">11.2.6.6. N4JS DI @Provides</a></li>
<li><a href="extended_fetaures.html#_n4js-di-inject">11.2.6.7. N4JS DI @Inject</a></li>
<li><a href="extended_fetaures.html#_n4js-di-singleton">11.2.6.8. N4JS DI @Singleton</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="extended_fetaures.html#_test-support">11.3. Test Support</a></li>
<li><a href="extended_fetaures.html#_polyfill-definitions">11.4. Polyfill Definitions</a>
<ul class="sectlevel3">
<li><a href="extended_fetaures.html#_runtime-polyfill-definitions">11.4.1. Runtime Polyfill Definitions</a></li>
<li><a href="extended_fetaures.html#_static-polyfill-definitions">11.4.2. Static Polyfill Definitions</a></li>
<li><a href="extended_fetaures.html#_transpiling-static-polyfilled-classes">11.4.3. Transpiling static polyfilled classes</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="components.html#_components">12. Components</a>
<ul class="sectlevel2">
<li><a href="components.html#_overview-2">12.1. Overview</a></li>
<li><a href="components.html#Component_Types">12.2. Component Types</a>
<ul class="sectlevel3">
<li><a href="components.html#_libraries">12.2.1. Libraries</a></li>
<li><a href="components.html#_runtime-environment-and-runtime-libraries">12.2.2. Runtime Environment and Runtime Libraries</a></li>
<li><a href="components.html#_tests">12.2.3. Tests</a></li>
<li><a href="components.html#_type-definitions">12.2.4. Type Definitions</a></li>
</ul>
</li>
<li><a href="components.html#package-json">12.3. Package.json File</a>
<ul class="sectlevel3">
<li><a href="components.html#_basic-properties">12.3.1. Basic Properties</a></li>
<li><a href="components.html#_n4js-properties">12.3.2. N4JS Properties</a></li>
<li><a href="components.html#_constraints">12.3.3. Constraints</a></li>
</ul>
</li>
<li><a href="components.html#_support-for-npm-scopes">12.4. Support for NPM Scopes</a></li>
<li><a href="components.html#sec:N4JS-Type-Definitions">12.5. N4JS Type Definitions</a>
<ul class="sectlevel3">
<li><a href="components.html#_specify-type-definition">12.5.1. Specify Type Definition</a></li>
<li><a href="components.html#_name-conventions">12.5.2. Name Conventions</a></li>
<li><a href="components.html#_version-conventions">12.5.3. Version Conventions</a>
<ul class="sectlevel4">
<li><a href="components.html#_define-a-new-type-definition-package">12.5.3.1. Define a New Type Definition Package</a></li>
<li><a href="components.html#_using-a-type-definition-package">12.5.3.2. Using a Type Definition Package</a></li>
<li><a href="components.html#_rational">12.5.3.3. Rational</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="components.html#_modules">12.6. Modules</a></li>
<li><a href="components.html#_api-and-implementation-component">12.7. API and Implementation Component</a>
<ul class="sectlevel3">
<li><a href="components.html#_execution-of-api-and-implementation-components">12.7.1. Execution of API and Implementation Components</a></li>
<li><a href="components.html#_api-and-implementation-with-di">12.7.2. API and Implementation With DI</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="plainjs.html#_plainjs">13. PlainJS</a>
<ul class="sectlevel2">
<li><a href="plainjs.html#_type-inference-and-validation-for-plain-js">13.1. Type Inference and Validation for Plain JS</a></li>
<li><a href="plainjs.html#_external-declarations">13.2. External Declarations</a>
<ul class="sectlevel3">
<li><a href="plainjs.html#_declaring-externals">13.2.1. Declaring externals</a></li>
<li><a href="plainjs.html#_instantiating-external-classes">13.2.2. Instantiating external classes</a></li>
<li><a href="plainjs.html#_implementation-of-external-declarations">13.2.3. Implementation of External Declarations</a></li>
<li><a href="plainjs.html#_example">13.2.4. Example</a></li>
</ul>
</li>
<li><a href="plainjs.html#_global-definitions">13.3. Global Definitions</a></li>
<li><a href="plainjs.html#_runtime-definitions">13.4. Runtime Definitions</a></li>
<li><a href="plainjs.html#_applying-polyfills">13.5. Applying Polyfills</a></li>
</ul>
</li>
<li><a href="jsdoc.html#_jsdoc-2">14. JSDoc</a>
<ul class="sectlevel2">
<li><a href="jsdoc.html#_general-n4jsdoc-features">14.1. General N4JSDoc Features</a>
<ul class="sectlevel3">
<li><a href="jsdoc.html#_provided-inline-tags">14.1.1. Provided Inline Tags</a>
<ul class="sectlevel4">
<li><a href="jsdoc.html#jsdoc_tag__code">14.1.1.1. @code</a></li>
<li><a href="jsdoc.html#jsdoc_tag__link">14.1.1.2. @link</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="jsdoc.html#_n4jsdoc-for-user-projects">14.2. N4JSdoc for User Projects</a>
<ul class="sectlevel3">
<li><a href="jsdoc.html#_standard-tags">14.2.1. Standard Tags</a>
<ul class="sectlevel4">
<li><a href="jsdoc.html#_-author">14.2.1.1. @author</a></li>
<li><a href="jsdoc.html#jsdoc_tag_param">14.2.1.2. @param</a></li>
<li><a href="jsdoc.html#jsdoc_tag_return">14.2.1.3. @return</a></li>
</ul>
</li>
<li><a href="jsdoc.html#_test-related-tags">14.2.2. Test Related Tags</a>
<ul class="sectlevel4">
<li><a href="jsdoc.html#jsdoc_tag__testee">14.2.2.1. @testee</a></li>
<li><a href="jsdoc.html#jsdoc_tag__testeeFromType">14.2.2.2. @testeeFromType</a></li>
<li><a href="jsdoc.html#_testeeType_and__testeeMember">14.2.2.3. @testeeType and @testeeMember</a></li>
<li><a href="jsdoc.html#jsdoc_tag_reqid_in_Tests">14.2.2.4. @reqid in Tests</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="jsdoc.html#_n4jsdoc-for-api-and-implementation-projects">14.3. N4JSDoc for API and Implementation Projects</a>
<ul class="sectlevel3">
<li><a href="jsdoc.html#jsdoc_tag__apiNote">14.3.1. @apiNote</a></li>
<li><a href="jsdoc.html#API_Project_Tags">14.3.2. API Project Tags</a>
<ul class="sectlevel4">
<li><a href="jsdoc.html#jsdoc_tag_apiState">14.3.2.1. @apiState</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="jsx.html#_jsx">15. JSX</a>
<ul class="sectlevel2">
<li><a href="jsx.html#_jsx-support">15.1. JSX Support</a></li>
<li><a href="jsx.html#_jsx-backend">15.2. JSX Backend</a></li>
</ul>
</li>
<li><a href="grammars.html#_grammars">16. Grammars</a>
<ul class="sectlevel2">
<li><a href="grammars.html#_type-expressions-grammar">16.1. Type Expressions Grammar</a></li>
<li><a href="grammars.html#_n4js-language-grammar">16.2. N4JS Language Grammar</a></li>
</ul>
</li>
<li><a href="jsobjects.html#_jsobjects">17. JSObjects</a>
<ul class="sectlevel2">
<li><a href="jsobjects.html#_object">17.1. Object</a></li>
<li><a href="jsobjects.html#_string">17.2. String</a></li>
<li><a href="jsobjects.html#_boolean">17.3. Boolean</a></li>
<li><a href="jsobjects.html#_number">17.4. Number</a>
<ul class="sectlevel3">
<li><a href="jsobjects.html#_static-attributes">17.4.1. Static Attributes</a></li>
</ul>
</li>
<li><a href="jsobjects.html#function">17.5. Function</a></li>
<li><a href="jsobjects.html#_error">17.6. Error</a></li>
<li><a href="jsobjects.html#_array">17.7. Array</a></li>
<li><a href="jsobjects.html#_date">17.8. Date</a></li>
<li><a href="jsobjects.html#_math">17.9. Math</a>
<ul class="sectlevel3">
<li><a href="jsobjects.html#static-attributes-1">17.9.1. Static Attributes</a></li>
</ul>
</li>
<li><a href="jsobjects.html#_regexp">17.10. RegExp</a></li>
<li><a href="jsobjects.html#_json">17.11. JSON</a></li>
</ul>
</li>
<li><a href="n4js_objects.html#_n4js-objects">18. N4JS Objects</a>
<ul class="sectlevel2">
<li><a href="n4js_objects.html#_reflection-model">18.1. Reflection Model</a></li>
<li><a href="n4js_objects.html#_error-types">18.2. Error Types</a>
<ul class="sectlevel3">
<li><a href="n4js_objects.html#_n4apinotimplemented">18.2.1. N4ApiNotImplemented</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="appendix_a_acronyms.html#_acronyms">Appendix A: Acronyms</a></li>
<li><a href="appendix_b_license.html#sec:License">Appendix B: License</a></li>
<li><a href="appendix_c_bibliography.html#_bibliography">Appendix C: Bibliography</a></li>
</ul>
</div>
</div>
<div id="content"><div class="sect1">
<h2 id="_annotations"><a class="anchor" href="#_annotations"></a><a class="link" href="#_annotations">10. Annotations</a></h2>
<div class="sectionbody">
<div class="sect2 language-n4js">
<h3 id="_introduction-2"><a class="anchor" href="#_introduction-2"></a><a class="link" href="#_introduction-2">10.1. Introduction</a></h3>
<div class="paragraph">
<p>Annotations are used to further define meta properties of language elements such as types, variables and functions.
These annotations are used by the compiler and validator to prohibit the developer from introducing constructs which are either not allowed or are unnecessary in certain contexts.</p>
</div>
<div class="paragraph">
<p>Since annotations are to be processed by the compiler and the compilation cannot be extended by third-party users for security reasons, annotations cannot be defined by developers.
Instead, the compiler comes with a predefined set of annotations which are summarized here.</p>
</div>
<div class="sect3">
<h4 id="_syntax-13"><a class="anchor" href="#_syntax-13"></a><a class="link" href="#_syntax-13">10.1.1. Syntax</a></h4>
<div class="paragraph">
<p>Annotations are used similarly as in Java (although new annotations cannot be defined by the user).
They are formally defined as follows:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-xtext" data-lang="xtext">Annotation:'@' AnnotationNoAtSign;
ScriptAnnotation returns Annotation: '@@' AnnotationNoAtSign;

AnnotationNoAtSign returns Annotation:
    name=AnnotationName (=&gt; '(' (args+=AnnotationArgument (',' args+=AnnotationArgument)*)? ')')?;

AnnotationArgument:
    LiteralAnnotationArgument | TypeRefAnnotationArgument
;

LiteralAnnotationArgument:
    literal=Literal
;

TypeRefAnnotationArgument:
    typeRef=TypeRef
;</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_properties-7"><a class="anchor" href="#_properties-7"></a><a class="link" href="#_properties-7">10.1.2. Properties</a></h4>
<div class="paragraph">
<p>We use the map notation for retrieving annotation properties and values from a list of annotations,
for example <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>.</mo><mi>a</mi><mi>n</mi><mi>n</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>t</mi><mi>i</mi><mi>o</mi><mi>n</mi><mi>s</mi><mfenced close="]" open="["><mrow><mi>R</mi><mi>e</mi><mi>q</mi><mi>u</mi><mi>i</mi><mi>r</mi><mi>e</mi><mi>d</mi></mrow></mfenced></math>, or shorter <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mi>@</mi><mi>R</mi><mi>e</mi><mi>q</mi><mi>u</mi><mi>i</mi><mi>r</mi><mi>e</mi><mi>d</mi></math>.</p>
</div>
<div style="page-break-after: always;"></div>
</div>
<div class="sect3">
<h4 id="_element-specific-annotations"><a class="anchor" href="#_element-specific-annotations"></a><a class="link" href="#_element-specific-annotations">10.1.3. Element-Specific Annotations</a></h4>
<div class="paragraph">
<p>The following annotations are element-specific and are explained in the corresponding sections:</p>
</div>
<table class="tableblock frame-all grid-all spread">
<caption class="title">Table 11. Element-Specific Annotations</caption>
<colgroup>
<col style="width: 33.3333%;">
<col style="width: 33.3333%;">
<col style="width: 33.3334%;">
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">Annotation</th>
<th class="tableblock halign-center valign-top">Element Types</th>
<th class="tableblock halign-left valign-top">Section</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Internal</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>TypeDefiningElement, Member, Function, Export</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="names.html#_access-control">Access Control</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Undefined</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Variable</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="types.html#_undefined-type">Undefined Type</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@StringBased</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Enum</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="types.html#_string-based-enums">String-Based Enums</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Final</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Class, Member</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="classifiers.html#_final-methods">Final Methods</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Spec</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>FPar</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="classifiers.html#Req-IDE-59">[Req-IDE-59]</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Override</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Method</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="classifiers.html#_redefinition-of-members">Redefinition of Members</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Promisifiable</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Function</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="functions.html#_promisifiable-functions">Promisifiable Functions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Promisify</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>CallExpression</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="functions.html#_promisifiable-functions">Promisifiable Functions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@This</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Function</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="grammar.html#_this-keyword">This Keyword</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@N4JS</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Class, Export Statement</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="plainjs.html#_external-declarations">External Declarations</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@IgnoreImplementation</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Script, ExportDeclaration, ExportableElement</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="plainjs.html#_external-declarations">External Declarations</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Global</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>External Declaration</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="plainjs.html#_global-definitions">Global Definitions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@ProvidedByRuntime</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>External Declaration</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="plainjs.html#_runtime-definitions">Runtime Definitions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@TestAPI</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>TypeDefiningElement, Member</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="extended_fetaures.html#_test-support">Test Support</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Polyfill</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Class</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="extended_fetaures.html#_polyfill-definitions">Polyfill Definitions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@StaticPolyfill</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Class</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="extended_fetaures.html#_static-polyfill-definitions">Static Polyfill Definitions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@StaticPolyfillAware</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Script</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="extended_fetaures.html#_static-polyfill-definitions">Static Polyfill Definitions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@StaticPolyfillModule</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Script</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><a href="extended_fetaures.html#_static-polyfill-definitions">Static Polyfill Definitions</a></p>
</div></div></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@Transient</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Field</code></p></td>
<td class="tableblock halign-left valign-top"><div><div class="paragraph">
<p><sup class="footnote">[<a id="_footnoteref_1" class="footnote" href="appendix_c_bibliography.html#_footnote_1" title="View footnote.">1</a>]</sup></p>
</div>
<div id="footnotes">
<hr>
<div class="footnote" id="_footnote_1">
<a href="#_footnoteref_1">1</a>. intended for internal use only; will be removed
</div>
</div></div></td>
</tr>
</tbody>
</table>
</div>
<div class="sect3">
<h4 id="_general-annotations"><a class="anchor" href="#_general-annotations"></a><a class="link" href="#_general-annotations">10.1.4. General Annotations</a></h4>
<div class="sect4">
<h5 id="_idebug"><a class="anchor" href="#_idebug"></a><a class="link" href="#_idebug">10.1.4.1. IDEBUG</a></h5>
<div class="paragraph">
<p><code>@IDEBUG</code> is an annotation similar to Java’s <code>@SuppressWarnings</code>.
It changes the severity of an issue from an error to a warning so that code can be compiled regardless of validation errors.
This is to be used for known IDE bugs only.</p>
</div>
</div>
</div>
<div class="sect3">
<h4 id="idebug-syntax"><a class="anchor" href="#idebug-syntax"></a><a class="link" href="#idebug-syntax">10.1.5. Syntax</a></h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-xtext" data-lang="xtext">'@IDEBUG' '(' bugID = INT ',' errorMessage=STRING ')'</code></pre>
</div>
</div>
<div class="paragraph">
<p>The annotation is defined transitively and repeatable on script, type declaration, function and method level.</p>
</div>
<div class="sect4">
<h5 id="_semantics-11"><a class="anchor" href="#_semantics-11"></a><a class="link" href="#_semantics-11">10.1.5.1. Semantics</a></h5>
<div class="paragraph">
<p>This annotation will cause errors issued in the scope of the annotation (in the defined script, type, or method) to be transformed to warnings if their message text is similar to the <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>e</mi><mi>r</mi><mi>r</mi><mi>o</mi><mi>r</mi><mi>M</mi><mi>e</mi><mi>s</mi><mi>s</mi><mi>a</mi><mi>g</mi><mi>e</mi></math> text.
If <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>e</mi><mi>r</mi><mi>r</mi><mi>o</mi><mi>r</mi><mi>M</mi><mi>e</mi><mi>s</mi><mi>s</mi><mi>a</mi><mi>g</mi><mi>e</mi></math> ends with <code>…</code> (three dots as a single character, created by Eclipse to abbreviate messages), then the error’s message text must start with the specified text.</p>
</div>
<div class="paragraph">
<p>If no matching error is found, the annotation itself will issue an error.</p>
</div>
<div id="ex:IDEBUG" class="exampleblock">
<div class="title">Example 98. IDEBUG Example</div>
<div class="content">
<div class="paragraph">
<p>In the following code snippet, two errors are to be transformed to warnings.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-n4js" data-lang="n4js">export class TestDataBridge with IModuleTest {
    @IDEBUG(166, "{function(number):void} is not a subtype of {function(T):void}.") <i class="conum" data-value="1"></i><b>(1)</b>
    @IDEBUG(91, "Incorrect number of arguments: expected 1, got 2.") <i class="conum" data-value="2"></i><b>(2)</b>
    @Override public run(): void {
        var foo = new Foo(),
            cb = function(val: number): void {},
            db = DataBridge.&lt;number&gt;bind(foo, "bar");
        db.add(cb); <i class="conum" data-value="3"></i><b>(3)</b>
        Assert.isTrue(called);
    }
}</code></pre>
</div>
</div>
<div class="colist arabic">
<table>
<tr>
<td><i class="conum" data-value="1"></i><b>1</b></td>
<td>The annotation transforms the error <code>{function(number):void} is not a subtype of {function(T):void}</code> into a warning with the following text:</td>
</tr>
<tr>
<td><i class="conum" data-value="2"></i><b>2</b></td>
<td>This annotation was proposed as a workaround for <a href="https://github.com/NumberFour/n4js/issues/91">IDEBUG-91</a> which has been fixed.<br>
No error message is produced and an error will be issued on this line instead:</td>
</tr>
<tr>
<td><i class="conum" data-value="3"></i><b>3</b></td>
<td>The first error occurs since there is a bug in the IDE type system (as of writing this example) where type arguments are not correctly bound in the case of function expressions used as callback methods.</td>
</tr>
</table>
</div>
</div>
</div>
</div>
<div class="sect4">
<h5 id="_suppress-warnings"><a class="anchor" href="#_suppress-warnings"></a><a class="link" href="#_suppress-warnings">10.1.5.2. Suppress Warnings</a></h5>
<div class="admonitionblock tip">
<table>
<tr>
<td class="icon">
<i class="fa icon-tip" title=""></i>
</td>
<td class="content">
This is not part of the current version
</td>
</tr>
</table>
</div>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_declaration-of-annotations"><a class="anchor" href="#_declaration-of-annotations"></a><a class="link" href="#_declaration-of-annotations">10.2. Declaration of Annotations</a></h3>
<div class="admonitionblock tip">
<table>
<tr>
<td class="icon">
<i class="fa icon-tip" title=""></i>
</td>
<td class="content">
This is not part of the current version
</td>
</tr>
</table>
</div>
</div>
</div>
</div>
</div>
<div id="footer">
<div id="footer-text">
Version 0.9<br>
Last updated 2019-08-08 13:15:33 CEST
</div>
</div>
<!-- ************* docinfo-footer *************************************************************** -->
<div class="Grid social" style="color:#d5dfea">
  <div class="Cell Cell--2-12 m-Cell--withMargin">
    <h2>Quick Links</h2>
    <ul>
      <li><a href="../downloads.html">Download</a></li>
      <li><a href="../userguides/index.html">Documentation</a></li>
      <li><a href="https://github.com/eclipse/n4js/">Source</a></li>
      <li><a href="https://github.com/eclipse/n4js/issues">Issues</a></li>
    </ul>
  </div>
  <div class="Cell Cell--2-12 m-Cell--withMargin">
    <br/><br/>
    <ul>
      <li><a href="https://www.eclipse.org/forums/index.php/f/365/">Forum</a></li>
      <li><a href="http://n4js.blogspot.de/">Blog</a></li>
      <li><a href="https://dev.eclipse.org/mailman/listinfo/n4js-dev">Mailing List</a></li>
      <li><a href="https://projects.eclipse.org/projects/technology.n4js">Eclipse Project Page</a></li>
      <li><a href="https://twitter.com/n4jsdev">Tweets by n4jsdev</a></li>
    </ul>
  </div>
  <div class="Cell Cell--2-12 m-Cell--withMargin">
    <br/><br/>
    <ul>
      <li><a href="http://www.eclipse.org/">Eclipse Home</a></li>
      <li><a href="http://www.eclipse.org/legal/privacy.php">Privacy Policy</a></li>
      <li><a href="http://www.eclipse.org/legal/termsofuse.php">Terms of Use</a></li>
      <li><a href="http://www.eclipse.org/legal/copyright.php">Copyright Agent</a></li>
      <li><a href="http://www.eclipse.org/legal/">Legal</a></li>
    </ul>
  </div>
  <div style="clear: both; height: 0; overflow: hidden;"></div>
</div>

<!-- ************* UI Scripts ************* -->
<script type="text/javascript" src="scripts/back-to-top.js"></script>

<script type="text/javascript" src="scripts/treeview.js"></script>
<script type="text/javascript" src="scripts/toc.js"></script>

<!-- ************* Prism.js Syntax Highlighting ************* -->
<script src="scripts/prism.js"></script>

<script type="text/javascript">
	// Add the 'toclist' id for search function
	$(".toc2 > ul").attr('id', 'toclist');
	// Generate a Search input form
	$("#toclist > li:first-of-type").before('<input type="text" id="pagesearch" onkeyup="search()" placeholder="Search for section...">');
	$("#toclist > li:first-of-type").before('<i id="clear" class="fa fa-times-circle-o"></i>');
	$("#clear").click(function(){
	    $("#pagesearch").val('');
	    search();
	    $('.toc2 > ul').treeView('collapseAll');
	});
	// intialize Treeview.js
	$(".toc2 > ul").treeView();
	// Initialize Scrollspy
</script>
<!-- ************* docinfo-footer *************************************************************** -->
</body>
</html>